GS-D500A datasheet(8/10 Pages) STMICROELECTRONICS

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A4 - SETTING OF THE DIRECTION POLARITY

The rotation direction signal must be applied at pin

J3-3.

The direction (CW or CCW) depends on the status

of the direction signal as shown in the following

table:

DIR. SIGNAL

ROTATION

HIGH

CCW

LOW

A5 - PHASE CURRENT PROGRAMMING

The phase current can be programmed by means

two on-board trimmer called R42 and R43 (see

mechanical drawing).

R42 programs the current in phase AB, while R43

programs the current in phase CD.

A6 - MIDRANGE STABILITY

A particular circuitry is implemented on the board to

avoid midrange oscillations.

This circuit is inserted on the current control loop

when SW5 is OFF.

A 7

C UR RE NT

SEL EC TI ON

I N

MI-

CROSTEP/CONSTANT CURRENT SWITCHING

(SW4)

When the board is used to drive a motor in mi-

crostep mode, an automatic switching from sinusoi-

dal/cosinusoidal current to consta nt current is

performed when the sinusoidal output wave-

form excee ds 500Hz. The constant output cur-

rent can be chosen to be 0.707 of the peak

current or the peak current: this possibility is

givenby SW4. (Seefig. 8).

SW4 OFF

0.707 x Ipeak

SW4 ON

Ipeak

Figure 8. Current selection by SW4

An histeresys is inserted on the 500Hz threshold to

avoid unwanted oscillations.

GS-D500A

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